1. Field of the Invention
This invention relates to a display apparatus for displaying characters, still images, moving images and other forms of information and it also relates to a video information display system for which such an apparatus can be suitably used.
2. Related Background Art
In recent years, a variety of handy apparatus adapted for use in multimedia environment have been developed and commercialized. Portable terminals and lap-top computers are among them. These apparatus can be used to retrieve information at locations other than offices and are also provided with capabilities of processing and transmitting information.
However, such apparatus are mostly designed for personal use and not adapted for teleconferences where a large number of attendants discuss subject matters in multimedia environment on the basis of commonly shared visual pieces of information. Thus, despite the development of such apparatus, people are forced to physically travel over a long distance at the cost of productivity in order to attend a meeting to be held at a single location.
Proposals have been made to xe2x80x9celectronizexe2x80x9d conferences and realize video conference systems. However, such systems are mostly designed for teleconferences attended by people stationed at different remote locations, where attendants can see each other and look at displayed data but cannot write-in and/or otherwise process data to update the information they have. Probably, this is mainly because no technology is currently available to instantly display updated information with a level of resolution and brightness comparable to that of the overhead projector (OHP) at a reasonable cost. Meanwhile, with a currently known visual telephone system, although two parties located at the opposite ends of the line can look at and talk to each other, neither of them can access the source of information possessed by the other party in order to write, erase and/or otherwise process data for the other party.
As for a projection type display apparatus, Japanese Patent Application Laid-open No. 54-139569 discloses a display apparatus comprising a light valve and a schlieren optical system for projecting an image as the light valve receives light. It additionally comprises a liquid crystal layer that produces a spheric and periodic structure that diffracts the flux of light directed to the light valve when a voltage is applied to the layer.
The above apparatus operates satisfactorily in terms of diffraction effect so long as the light valve is sufficiently large and a high degree of resolution is not required for it and, at the same time, the cell size of each pixel is large. To the contrary, however, when the light valve is relatively small and required to show an enhanced degree of resolution and still the cell size of each pixel is as small as tens of several micrometers, the diffracting zone is made extremely narrow and no sufficient amount of diffracted light becomes available to remarkably lower the level of brightness and contrast.
Japanese Patent Application Laid-open No. 61-167297 discloses a display apparatus comprising a plurality of liquid crystal panels arranged to a multilayer structure in order to display bright images on the screen. However, the apparatus is still unsatisfactory in terms of the absolute brightness of the displayed images mainly because three primary colors are overlaid one on the other for displaying color images.
Therefore, it is an object of the present invention to provide a video information display system that can be suitably used for a video conference system and with which the attendants of the video conference may access to and share common sources of information.
Another object of the invention is to provide a display apparatus that can be suitably used for such a system.
Still another object of the invention is to provide a video display apparatus that can display images with a level of resolution and brightness comparable to that of an OHP and that can be manufactured at reasonable cost.
A further object of the invention is to provide a video display apparatus comprising a large and high definition display screen and capable of simultaneously displaying different visual pieces of information from a plurality of different sources selectively in color or in black and white on a divided screen such that each visual piece of information may be dimensionally enlarged or reduced at will within the display screen.
According to a first aspect of the invention, the above objects are achieved by providing a video information display system for receiving data for video information entered from a plurality of sources and displaying the video information after synthetically combining and/or editing the data, characterized in that said system comprises
means for synthetically combining and/or editing data according to control signals from the sources of video information,
first video information display means for displaying on the side of the plurality of the sources the video information and
second video information display means to be placed at a location different from that of the first video information displaying means for displaying video information obtained by synthetically combining and/or editing data.
According to a second aspect of the invention, there is provided a display apparatus for displaying video information by superimposing a plurality of images obtained through a plurality of display systems, each being constituted by a light source, a reflection type liquid crystal panel and an optical system, characterized in that said apparatus comprises at least either of
system selection means for selecting at least one of the plurality of display systems, and
modification means for modifying the attributes of the image obtained through said at least one of the display systems.
With a video information display system and a display apparatus according to the invention, attendants of a conference can share sources of information and process information stored there.
With a video information display system and a display apparatus according to the invention, attendants of a teleconference including those located in remote areas can share sources of information and process information stored there by writing and other processing means to successfully hold the conference.
A display apparatus according to the invention can display images in black and white or in color or in both black and white and in color at the user""s will and the user of the apparatus can use it to exchange data with terminals of other information systems and process data. Thus, the attendants of a conference where a display apparatus according to the invention is used can freely share sources of information to improve the efficiency of the conference. Additionally, since a display apparatus according to the invention is compact and can be manufactured at low cost, it provides a convenience for office environment.
In a display apparatus according to the invention, means for modifying the attributes of an image comprises means for changing the color or colors of the image, means for changing the size of the image and means for changing the brightness of the image.
With a display apparatus according to the invention, one of a plurality of display systems may be used for displaying an image in black and white while the remaining systems are used for displaying images in different colors. These images may be superimposed on each other on a single display screen so that one or more than one images may be displayed in black and white while the remaining images are displayed in different colors simultaneously.
The color filters arranged on the light paths of the color display systems can be operated either in set or non-set mode so that they may also be used to display images in black and white. If they are used for displaying images both in color and in black and white simultaneously, the display systems for displaying images in black and white are made to generate black and white image signals including a black signal for reserving an area on the display screen for color images, whereas the display systems for displaying images in color are made to generate color image signals including a black signal for reserving an area on the display screen for black and white images.
For the purpose of the present invention, the area for black and white images or the area for color images of the display screen may be selectively illuminated by rays of light from the light source by means of a liquid crystal panel or by some other means in order to ameliorate the quality of the image.
In a display apparatus according to the invention, the optical system of each display system may comprise a schlieren optical system. Additionally, it may comprise a panel provided with a mirror and a pinhole arranged on the focal point of the lens disposed on the liquid crystal panel of the system. The liquid crystal panel may preferably be of polymer type. Preferably, the liquid crystal panel is provided with an anti-reflection film on the surface of the transparent substrate for receiving incoming flux of light from the light source and on the rear side of the liquid crystal panel in order to reduce noise.
If the optical axis of the optical system of a display apparatus according to the invention is inclined relative to the surface of the display screen for displaying projected images and if, when measured along the optical axis of the aggregate optical system, the largest distance between the display screen and the exit pupil is b2 and the smallest distance between the display screen and the exit pupil is b1 while the largest distance between the liquid crystal panel and the entrance pupil of the optical system is a1 and the smallest distance between the liquid crystal panel and the entrance pupil of the optical system is a2, an agreeable image free from distortions and blurs can be obtained on the display screen by minimizing the difference between b1/a1 and b2/a2.
A display apparatus according to the invention can be down-sized and manufactured at low cost by using polycrystalline Si thin film transistors for the pixel section of the liquid crystal panel and bulk Si transistors for the peripheral circuits.
A display apparatus according to the invention preferably comprises means for transmitting data for video information to information terminals and an image processing circuit section provided with memories and means for compressing, expanding, encoding and decoding data. Preferably, video signals for an odd row of pixels and for an adjacent even row of pixels are transmitted simultaneously to the liquid crystal panel from the image processing circuit section and a drive line is arranged between each pair of an odd row and an even row and signal lines for odd rows and those for even rows are alternately arranged.
For a display apparatus according to the invention, wireless interfaces may advantageously be provided.